GB1593427A

GB1593427A - Screening plant for removing suspended solid materials from liquids

Info

Publication number: GB1593427A
Application number: GB43105/77A
Authority: GB
Original assignee: Maschinenfabrik Hellmut Geiger GmbH and Co KG
Current assignee: Brackett Geiger GmbH and Co KG
Priority date: 1976-10-21
Filing date: 1977-10-17
Publication date: 1981-07-15
Also published as: JPS61127B2; US4184957A; AT353197B; CH622304A5; ATA691977A; AU2988577A; DE2647539A1; DE2647539C2; FR2368443A1; JPS5354366A; BR7707049A; SE7711200L; NL7711496A

Description

PATENT SPECIFICATION

( 21) Application No 43105/77 ( 22) Filed 17 Oct 1977 ( 31) Convention Application No 2647539 ( 32) Filed 21 Oct.

( 33) Fed Rep of Germany (DE) ( 11) 1 593 427 ( 19) 1976 in 4 Complete Specification Published 15 Jul 1981

INT CL 3 B Ol D 35/02 Index at Acceptance B 1 i D 1505 1816 1906 2104 2111 T ( 54) SCREENING PLANT FOR REMOVING SUSPENDED SOLID MATERIALS FROM LIQUIDS ( 71) We, MASCHINENFABRIK HELLMUT GEIGER Gmb H & Co KG, of D 7500 Karlsruhe, a Company organized under the laws of the Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

The invention relates to a screening plant for removing suspended solid materials from liquids, consisting of a first apparatus for retaining the materials and a second apparatus for taking the materials out of the liquid Such screening plants are usually provided in the intake structures of sewage treatment plants, cooling water intake plants etc, in order to conduct the liquid to the individual process stages without disturbances which would be caused by suspended solid materials.

Multi-stage screening plants are usually constructed in such a fashion that a plurality of screening units are arranged one behind the other and each unit comprises: an apparatus for retaining the suspended materials, that is to say a screen or the like, and an apparatus for taking out the materials, that is to say a rake cleaning device which travels up and down or rotates, and an apparatus for conveying onwards the materials which form the screenings In other words the outlay involved in a multi-stage screening plant is approximately proportional to the number of stages This outlay comprises equally the aspects of space requirements, machine technology, control technique, maintenance and price.

This outlay may be reduced by using a single cleaning apparatus to clean, in succession, screens which are arranged in a spaced relationship But this requires complicated mechanical measures Also the time required for cleaning is twice as great as would be required for cleaning only a single screen.

An object of the present invention is to provide an improved screening plant to reduce this outlay and this is substantially achieved in that, in multi-stage screening plants, the apparatus for retaining the coarse materials comprises two screens (first and second in the direction of liquid flow) situated adjacent each other and one behind the other, and the apparatus for taking out the materials comprises a screen cleaner having a rake which extends through at least one of the screens and strips off the materials from both screens in the same working operation Other features according to the present invention are mentioned in the subordinate claims.

The underlying idea of the present invention makes it possible to provide a, for example, two-stage screening plant with the outlay of a single-stage screening plant All parts of the plant except for the actual screen are provided only once, although the effect of the plant corresponds to that of a two-stage plant.

The arrangements and relationships of the screens are of particular advantage.

With the first screen projecting freely upwards, the stripped-off screenings are conducted upwards at the end of the screen bars without falling back into the channel In the event of a differential head because of the blocking of the screen and subsequent flooding over the first screen there is no risk of the screenings flowing through the plant.

The first screen can be regarded as an overload protection arrangement for the entire plant: a specific quantity of screenings will tend to block two screens to a lesser extent than one screen Various advantages follow therefrom: in the case of deep screening plants with long travel distances and therefore considerable cleaning periods, the invention affords good safety against overloading; under normal conditions, larger ir ( 44) ( 51) ( 52) 2 1 593 427 2 quantities of screenings can be taken off.

If the first screen is taken only about as far as the average liquid surface level, reserve capability is provided as regards blocking for higher liquid levels, and there is better access to the screens.

If the bars of at least the second screen reach to above the highest liquid surface level, it is ensured that the channel is reliably closed by the screen If the bars reach to above the discharge height, they can be connected to one another in that region by a cross-head.

To separate out relatively large quantities of screenings, it is advantageous to make the gap width of the second screen smaller than the gap width of the first screen.

It is also advantageous, in engagement of the rake at the side of the screen against which the flow moves, to make the spacing of the teeth of the rake correspond to the engagement thereof in the screens: in the front region in accordance with the pitch of the second screen, in the rear region in accordance with the pitch of the first screen.

It is also particularly advantageous to give the first screen a greater inclination than the second screen because of the coarser nature of the materials which are deposited there.

The first screen may be inclined at approximately 10 to 300 and the second screen at approximately O to 10 .

The invention will now be described, by way of example, with reference to the accompanying drawings wherein:

Figure 1 shows a diagrammatic longitudinal section through a screening plant with engagement of the rake at the side of the screen at which the flow arrives; and Figure 2 shows a diagrammatic longitudinal section through a screening plant with engagement of the rake oppositely to the direction of incident flow.

In Figure 1 and Figure 2, the liquid 7 flows in the channel 5 through the screens 1 and 2 which are situated adjacent each other and one behind the other Suspended solid materials contained in the liquid 7 are retained at the two screens 1 and 2 and form the screenings 16 and 17 The screens 1 and 2 are secured with the fixing device or anchorage 21 in the channel bottom 4 and either project freely upwards ( 1) or are combined constructionally above, like the screen 2 in Figure 1 in an apron 22 of the structure or in Figure 2 in a cross-hand 23 above the discharge region.

The screens 1 and 2 are cleaned by a screen cleaner This comprises a cleaning carriage 13 and the rake 3 linked thereto.

The cycle of movement of the rake 3 is brought about by guiding the carriage 13 in straight guideways 14 and oval guideways 15, and in the illustrated example the carriage 13 is driven by means of a driving pinion 19 and a gear rack 20.

In Figure 1, the rake 3 engages in the vicinity of the channel bottom 4 in the direction of flow of the liquid 7, the rake projecting through the first screen 1 and into the second screen 2 On moving further, in the cleaning direction 18, the rake 3 strips of the screenings 16 from the screen 1 and strips off the screenings 17 from the screen 2, and takes the material upwards above the surface 8 of the liquid and along the apron 22 Arranged above the service floor 6 is a stripping device 11 which strips the screenings from the rake 3 and discharges them into the disposal container 12.

In Figure 2 the rake 3 engages in the vicinity of the channel bottom 4 oppositely to the direction of incident flow 7, the rake projecting both through the second screen and through the first screen 1, and on moving upwards, in the cleaning direction 18, the rake strips the screenings 16 and 17 from the screens 1 and 2 Here again the screenings are taken upwards, above the surface 8 of the liquid, to be discharged.

When the rake 3 is drawn back for downward movement, the stripping device 11 pushes the screenings from the rake 3 so that they fall over the swung-in chute 10 and into-the disposal container 12 It is possible to use proportions which are other than those shown in here in accordance with the desired discharge height 9.

More particularly the invention is not limited to the screen cleaner shown here It is also possible for the usual driving systems using ropes and chains, travelling upwards and downwards or in a rotary fashion, to be used appropriately with advantage.

Claims

WHAT WE CLAIM IS -

1 Screening plant for removing suspended solid materials from flowing liquids, comprising a first apparatus for retaining the materials, and a second apparatus for taking the materials out of the liquid, wherein the first apparatus comprises two screens (first and second in the direction of liquid flow) situated adjacent each other and one behind the other, and the second apparatus comprises a screen cleaner having a rake which projects through at least one of the screens and strips off the materials (screenings) from both screens in the same working operation.

2 Screening plant according to claim 1, wherein the first screen comprises screen bars which are secured in the bed of a channel for the liquid and project freely upwards.

3 Screening plant according to claim 2, wherein the bars of the first screen project to approximately the height of the average liquid surface level.

4 Screening plant according to any one of claims 1 to 3, wherein the second also 1 593 427 1 593 427 comprises screen bars and at least the bars of the second screen project above the highest water level.

Screening plant according to claim 4, wherein the bars of the second screen project above the discharge height to which the rake raises the screenings.

6 Screening plant according to any one of claims 1 to 5, wherein, the screens comprising screen bars, the bar spacing of the second screen is smaller than the bar spacing of the first screen.

7 Screening plant according to claim 6, with the rake acting on the incident flow side of the screens, wherein the tooth pitch of the rake in the front region of the rake corresponds to the pitch of the second screen and in the rear region to the pitch of the first screen.

8 Screening plant according to any one of claims 1 to 7, wherein the first screen is given a greater inclination to the vertical in the direction of flow than the second screen.

9 Screening plant according to claim 8, wherein the first screen is inclined at 100 to 300 to the vertical, and the second screen at 00 to 100 to the vertical.

Screening plant substantially as herein described with reference to the accompanying drawings.

STANLEY, POPPLEWELL, FRANCIS & ROSS, Chartered Patent Agents, 1, Dyers Buildings, Holborn, London, EC 1 N 2 JT.

Agents for the Applicants Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1981.

Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.